Trainer for enabling the giving of radio instruction



July 25, 1950 A, LUDWIG 2,516,780

TRAINER FOR ENABLING THE GIVING oF RADIO INSTRUCTION Filed DBG. 9, 1944 12 Sheets-Sheet l /N VEN TOR LUDW/G A TTO'QNEV A. LUDWIG 2,516,780

12 Sheets-Sheet 2 0F RADIO INSTRUCTION TRAINER FOR ENABLING THE GIVING July 25, 1950 Filed Dec. 9, 1944 ATTORNEY A. LUDWIG 2,516,780 TRAINER FOR ENABLING THE GIVING 0F RADIO INSTRUCTION 12 Sheets-Sheet 3 /NVENTOR B. A. LUDW/G ATTORNEY July 25, 1950 Filed Dec. 9, 1944 July 25, 1950 A. LUDWIG 2,516,780

TRAINER FOR ENABLING THE GIVING OF RADIO INSTRUCTION Filed Dec. 9. 1944 12 Sheets-Sheet 4 SNN /N VEN TOR BV ,4. wow/c 6? 6. mbi- A TTORNE Y July 25 1950 A. LUDWIG 2,516,780

TRAINER FoR ENABLING THE GIvING oF RADIO INSTRUCTION Filed Dee. `9; 1944 l2 Sheets-Sheet 5 A 7' TORNEV July 25, 195o A. UDwiG 2,516,780

TRAINER FOR ENABLING THE GIVING OF RADIO lINSTRUCTION Filed Dec. 9, 1 944 l2 Sheecs--Sheetl 6 By @a M A TTOR/VEV m 7 nl.. .m e w w 5., .r 2 n e h s 2 1 Nd I v I GN o I @mm [GU wwwn BLM UmI wm AR mm mw I A m o w 5 1 mw 9. o. M.. d .J F

kk Nk wkn /NvENO/P ,4. LUDWIG N @Dx ATTORNEY July 25, 1950 A. LunwrG 2,516,780

TRAINER FOR ENABLING THE GIVING 0F RADIO INSTRUCTION Filed Dec. 9. 1944 12 Sheets-Sheet 8 COUPLNG M0 TUNING M0 RANGE /NVE/VTOR ,4. LUDW/G BV A ATTORNEY A. LUDWIG v TRAINER FOR ENABLING THE GIVING lHmy 25, 1950 OF RADIO INSTRUCTION Filed Dec. A9, v1944 l2 Sheets-Sheet 9 HHH Illlll Q 'n o.

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A r rom/Ev Juy 25 1950 A. LUDWIG TRAINER RoR ENABLING THE GIVING oF RADIO INSTRUCTION Filed Dec. 9, 1944 12 Sheets-Sheet 10 m62 I I I I l l l l I l l l I I l l I l I I I /NVENTOR A. ww/G A TTORNEV July.25, 1950 A. LUDWIG TRAINER FOR ENABLING THE GIVING 0F RADIO INSTRUCTION 12 Sheets-Sheet ll r-jiled Dee. 9, 1 944 lllllll Ill Il |||ll||||||l|ll|| Il.l ll .IIIIL /NVENTOR BV A. wow/c A 7` TORNEV July 25, 1950 A. LuDwlG 2,516,780

TRAINER RoR ENABLING THE GIVING oF RADIO INSTRUCTION Filed Dec. 9, 1944 12 Sheets-Sheet 12 /NVENTOR A. LUDW/G ATTORNEY Patented July 25, 1950 TRAINER FR ENABLING THE GIVING F RADIO INSTRUCTION Arthur Ludwig, Rockville Centre, N. Y., assigner to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application December 9, 1944, Serial No. 567,445

27 Claims. l

This invention relates to a radio transmitter and more particularly to the modification of a transmitter whereby it may 'be used in the training of radiomen in the proper tuning and use of a similar transmitter normally -used for regular radio transmission.

There are many instances where radio transmitter and receiving equipments are very important adjuncts to commercial, maritime and war activities and where therefore it is essential that radiomen be trained to handle them eiiiciently under all operating conditions One such instance, for example, is on airplanes. Modern airplanes, and particularly those of larger size requiring a crew of several men for their operation used in combat service, are equipped with one or more radio receivers which may be tuned to receive intra-squadron messages or messages from distant bases, with one or more radio transmitters which may be tuned to transmit which would be installed at a base of operations for transmission to airplanes and with monitoring equipment to enable the instructor to monitor on communications carried on over the interphone system of the trainer as though he were a member of the crew, to monitor on the operation of the radio receivers and transmitters of the trainer and to monitor on other operationsvof the communication equipment of the trainer asfmay be desired.. v

rThe present invention isl more particularly concerned with the modication of a radio transmitter of the typeused in an airplane for long range communication with distant bases, but to enable the better Visualization of the manner 'in 1 which the transmitter is coordinated with the messages to other airplanes in the same squadron or group or to more distant bases and with an interphone system to'enable the members ofthe crew to converse with each other.

For training an airplane crew to handle the communication equipment of the airplane and to best coordinate their efforts through the use of such equipment, it is proposed toprovide radio instruction equipment, This equipment may or may not be corollary to a trainer for giving the airplane crew flight training. However, if a night trainer is provided for the purpose of giving instruction in the flight operation of an airplane which the trainer is designed to simulate, it is desirable that provision also be made in such trainer for giving the crew training in the use of the communication equipment which would be installed in the airplane.

To enable training to be given in the use of the communication equipment of an airplane in connection with a flight trainer, as illustrated herein, the communication equipment which v,would be installed as the regular equipment of other portionof the communication system and with the radio instructors desk, the other portions of the communication system and the radio instructors desk `equipment areleither shown in detail or schematically herein. y

Since it isy not desirable lfor training purposes to radiate power from the transmitter into the ether, the transmitter is not connectable to radiating antenna systems but the oscillator equipment which is-arranged to transmit on any one of a plurality of carrier frequencies is carefully shielded and probes are provided within the shield, which probes are connected by acoaxial system with the instructors desk which system is connected to the inputs of the radio receivers at such desk. Since little power is required for transmission'over theshortcoaxial cable to the instructors desk, the power amplier equipment of the transmitter is eliminated and potentiometers operable from the regular tuning controls of the tranmsmitter and` electronic devices are provided for controlling the various meters of the transmitter in simulation of their usual response to the tuning of the transmitter. All of the operating and tuning controls are retained although they do not perform their usual functions so that the transmitter panelsk present their normal appearance and all vcontrols on such panels have the usual feel tothe operator and must be oper?- ated in the usual manner to produce readings on the meters indicativeoi the' efficiency at which the transmitter is being operated.

The oscillator equipment of the transmitter has been retained and is substantiallyr the same as ordinarily used. In the type of transmitter hereing illustrated two transmitter units are provided one for vhigh frequency range 'transmission' and the other for intermediate frequency transmission and each unit is provided with its own master oscillator equipment. As previously stated, this equipment is shielded to prevent direct radiation. In addition lter circuits are also provided in the power supply leads extending to each oscillator to prevent radiation therefrom and each oscillator is also provided with a potentiometer and range selector switch for use in the simulated control of the meters and suitably connected with the frequency tuning and range selection controls of the oscillator.

For a clearer understanding of the invention and the mode of its operation, reference may be had to the following detailed description when read in connection with the accompanying drawings in which:

Eig. 1 schematically discloses a flight trainer simulating the fuselage of an airplane, 'a night instructors desk, a radio instructors desk, the control bays in which control apparatus of the trainer is installed, and operating and communication cables interconnecting the trainer, the control bays and the instructors desks;

Figs; 2 and 3 taken together show the interphone system of the trainer;

Fig. 4 shows schematically the four radio receivers ofthe trainer, the remote control box for controlling two of such receivers, two of the short range radio transmitters of the trainer, the dynamotor and modulator units, the remote control box and the yantenna relay unit therefor, the frequency meter for use in preliminarily tuning the transmitters, junction boxes and iconductor and coaxial cables for interconnecting the various apparatus units of the trainer;

liligs` y5 yand 6 taken together show the apparatus and circuits mounted in the cabinet and on the panel of the high frequency unit of the modified long range transmitter, Fig. 5 showing the potentionieters and electronic devices responsive to the operation of the tuning controls of the usual amplifier stages of the transmitter, and Fig. Gshowing in the lower portion thereof and enclosed within the dot-dash lines, the modied oscillator equipment and in the remaining portion thereof additional potentiometers and switch equipment responsive to the operation 0f other tuning controls of the transmitter, and meters;

Fig; 'l shows the apparatus mounted in the cabinet and on the panel of the central or power unit of the transmitter, meters, control switches and jacks being-shown in the upper portion of the gure, the rectier equipment being shown in the right lower portion of the figure, and the modulator circuit for iuse in both the high and intermediate frequency units of the transmitter and additional controls being shown in the lower left portion of the figure;

Fig. 8 shows the apparatus and circuits mounted in the cabinet and on the panel of the intermediate frequency unit of the transmitter, the modified oscillator equipment being shown in the dot-dash rectangles in the lower portion of the gure and the potentiometers, switches and electronic devices responsive to the usual controls of the transmitter, and meters being shown in the remaining portion of the figure;

Fig. 9 shows schematically the four radioreceivers `at the instructors desk, the control turret on the desk, the front and cross-section of which have been illustrated, junction boxes and conductor and coaxial cables for interconnecting the various apparatus units at the instructcrs desk;

Fig. l0 shows in the lower left portion thereof the communication equipment located at the flight instructors desk whereby the flight instructor may communicate with the members of the crew in the trainer over the interphone system, in the lower central portion thereof, the receivers, transmitter and signal key and the connection plugs and jacks located atv the radio instructors desk and in the remaining portion of the gure the equipment located in the turret on the desk;

Fig. 11 shows within the rectangle in the left portion thereof the monitoring amplifier equipment, within the rectangle in the upper right portion thereof the regulated rectifier equipment and within the rectangle in the lower right portion thereof the Z50-volt rectiiier equipment, all located in the radio instructors desk;

Fig. 12 shows in the lower right portion thereof the transmitter modulator and in the remaining portion thereof the transmitter. oscillator units and the selection relays associated therewith located within the radio instructors desk; and

`Fig. 13 is a diagram showing how the other figures of the drawing should be arranged to completely disclose the invention.

Referring nrst to Fig. 1, a mock-up of the fuselage of an airplane is identified by the numeral 100, in which fuselage the various stations of the members of the crew are indicated, these stations comprising the pilots, co-pilots, flight engineers, navligators, bcmbardiers and radiomans station, all interconnectable over the usual interphone system as will later be described. The operational and night control equipment of the trainer is connected over control cable HH with the control bays 102 'and over control cable ids with the ight instructors desk illd which in turn is connected over control cable |05 with the control bays H32. The trainer mock-up |00 is also connected by a communication cable |05 with a distributing box at the night engineers desk |04 from which box a cable of conductors extends to the flight instructors interphone station lill and from which a connection over communication cable m8 is extended to the radio instriuctors desk lili). A station H0 at the control bays is also connected over communication cable i! i with the interphone system of the trainer, whereby communication with members of the crew and with the instructors may be carried on by the maintenance man at the control bays. The radio receivers and transmitters in the trainer are also connected with the radio receivers andY transmitters at the radio instructors desk by a coaxial cable H2.

The interphone system of the trainer, disclosed in Figs. 2 and 3, is substantially identical with that installed in an airplane of the type in which the trainer is designed to simulate but has been modified by the addition of cable 2% which extends from the distribution junction box 2G! to the terminal strip 292 o n the pilots panel from which the cable Hi extends to the interphone station H0 at the control bays |02. Terminals havealso been added to the terminal strips 301 and 3il2 in the interphone junction box 303 and a cable of conductors YH36 has been extended from terminals on the strips 381, 302 and 36B to the junction box [01 at the flight instructors desk 104.

As schematically disclosed in Fig. 4, two radio receivers 400 and 4M are mounted on the receiver racks 4U I and 495 which in turn are mounted in the trainer lill) on a rack above the radio.- mans station and are connected by cables 402 and 406 and plug and jack connectors 403 and 401 with the radio receiver junction box 408 located adjacent to the receivers. 27-volt direct current is supplied to these` receivers from the battery junction box 409 over the cable 4 I 0 which makes connection with the junction box 408 over the plug and jack connector 4I The inputs of these receivers are not connected in the usual manner with an antenna system but instead probes are inserted within the receiver casings and connected over coaxial cables 4|2 and 4|3 and the plug and jack connectors 4|4 and 4|5 with the coaxial junction box 4|6 located under the radiomans table. The radio receiver junction box 408 is provided with jacks 4|'| and 4|8 in which plug-ended cables 4|9 and 420 extending to terminals on the terminal strip 304 of the radiomans interphone control unit 300, Fig. 3, are inserted.

The output of the No. 1 receiver 400 is received over cable 420 and, with the selector switch 305 in position 1 and the switch 306 in either the on or OIT position this output is connected over the No. 1 contact of the switch arc 301, conductor 308, and the plug and jack connector 203 at the radiomans station box, with the right receiver of the radiomans headset 205, and the output of the No. 2 receiver 404 is received over cable 4|9 and, with the selector switch 305 in position 1 and the switch 306 in its interphone system-on position, this output is connected over the No. 1 contact of the switch arc 309 to'the primary winding of transformer T3, is impressed upon the amplifier tube AMP3, ampliiied thereby and impressed through the windings of output transformer T4, over the upper right contact of switch 306 and the No. 1 contact of switch arc 3I0, over conductor 3H and the plug and jack connector 204 at the radiomans station box with the left receiver of his headset 205, or if switch 306 is in its interphone system-oit position this output is applied over the lower right contact of switch 306 and the No. l contact of the switch arc 3|6 and thence as traced to the left receiver of the radiomans headset 205.

If the selector switch 305 is in position 2, the l No. l radio receiver is connected to the radiomans right headset receiver as previously described and reception from the interphone system is applied from the secondary winding of transformer T2, over the upper left contact of switch 306 if it is in its interphone-on position, over the No. 2 contact of switch arc 3I0 land thence as traced to the left receiver of the radiomans headset 205. If the selector switch 305 is in position 3, the No. 2 receiver is connected over the No. 3 contact of the arc 301 with the right receiver of the headset 205 in either position of switch 306 and with the switch 306 in its on position reception from the interphone system is applied from the secondary winding of transformer T2, over the upper left contact of switch 306 and the No. 3 contact of arc 3I0 to the left receiver of the radiomans headset 205. If the switch 305 is in position 4 and the switch 306 is in its on position, reception from the interphone system is applied over the upper left contact of switch 366 and the No. 4 contacts of arcs30`| and 3I0 to both receivers of the radiomans headset 205. If the switch 305 is in position 5, the No. 1 receiver 400 is connected over the No. 5 contacts of arcs 301 and 3I0 with both receivers ofthe headset 205 and if the switch 305 is in position 6 the No. 2 receiver 404 is connected over the No. 6

, contacts ofarcs 301 and 3I0 with both receivers of the headset 205. The switch 305 may thus be selectively operated by the radioman so that he may, over his two headset receivers, simultaneously listen in onboth radio receivers 400 and 404 or` on either radio receiver and the interphone system, and may listen in with both headset receivers onveither the interphone system, the No. 1 yradio receiver 400 or the No. 2 radio receiver 404.

Two other radio receivers 42| and 422 are equipped with receiver dynamotor units 423 and 424 which supply them with high positive anode potential and are mounted in a two-unit receiver rack 425 in turn mounted on a shelf above the ,.ight engineers station. These receivers may be operated singly or together by local tuning controls or may be remotely controlled over flexible-control cables 426 and 421 from the receiver control box 428. The receivers are also connected by the cables 429 and 436 which connect by plug and jack connectors 43| and 432 with thereceiver rack 425 and by plug and jack connectors 433 and 434 with the control box 428. Battery current from the 27-volt battery junction box 400 is supplied to these receivers over the cable 435 which is connected with the receiver rack 425 by a plug and jack connector 436.

The inputs of the radio receivers 42| and 422 are not connected in the usual manner with an antenna system but instead probes are inserted within vthe receiver casings and connected over coaxial cables 437 and 438 and the plug and jack connectors 439 and 440 with the coaxial junction box 44| located adjacent to the receivers 42| and 422. This junction box is connected over the coaxial cable 442 with the coaxial junction box 4|6. The cable 442 makes connection with the two junction boxes by the plug and jack connectors 443 and 444.

-The antenna binding posts 445 and 446 of the receivers 42| and 422 are connected to the receiver'binding post REC of the antenne relay unit 441 by cloth sleeving to simulate the usual connection of the receivers to the antenna relay unit. The use of wire for these connections would result in undesired radiation. When the frequency meter 450 is to be used in checking the frequency of the output of radio transmitters 452 and 453 of the trainer it receives power for its operation over the cord 449 connected by the plug 448 :with supply leads in the radio receiver 42|. To control the relays of the receiver rack 425 to cut orf the receivers when either transmitter 452 or 453 is being used, to supply operating ground from the relay rack 425 to the modulator unit 45| and to supply side-tone reception to the radio receivers 42| and 422 whenever either of the transmitters 452 and 453 is being used, the receivers are connected over the receiver rack 425 andthe cable 454 with the modulator unit 45|, the cable making connection with the receiver rack 425 by l the plug and jack connector 455 and with the jacks of` eithersection of the receiver control box Twotransmitters 452 and 453 are provided in the `trainer for'short distance'transmisson be- .,tween/airplanes of thefsame ,squadron prfgloup.

.atraveo These transmitters are mounted on a shelf vabove the Iii'ght enginecrs instrument panels and the transmitter control box 460 for remotely` controlling such transmitters is mounted on the pilots pedestal. The modulator unit 451 for these transmitters is mounted to the right of the transmitters 4and the antenna, relay unitv 441 is mounted above the transmitters. A cable461 connects the rack 462 upon which the transmitters are mounted with the modulator unit 451, such cable being connected to the rack and to 'the modulator unit by plug and jack connectors 969 and 964. Cable 465 -connects the transmitter rack 462 with the antenna relay unit 441, such cable being connected to the rack and to the antenna relay unit by plug and jack lconnectors 466 and 461.

The antennas of the transmitters are not used `for radiating energy but instead each transmitter is provided with a probe within its casing, the probe of transmitter 452 being connected to a coaxial cable 498 which is connected by the plug and jack connector 469 with the coaxial junction box 44! and the probe of transmitter 453 being connected to a coaxial cable 410 which is connected by the plug and jack connector 41.1 with The microphones of certain of the interphone station boxes are connectable to the modulator unit 451 over the cable 419 Vby the insertion vof the plug 411 of the cord circuit 418 extending to the pilots control box, Fig. 2, into the microphone jack MIC of the control box 460. The antenna binding posts of the transmitter are connected as shown to the TR binding post of the antenna relay unit `441 and the ANT binding post oi the antenna relay unit is connected to the 27-volt supply in the battery junction box 409.

The antenna relay unit 441, the transmitter l rack 462, one of the transmitters mounted thereon, for example transmitter 452, the modulator unit l4911 together with the associated dynamotor unit and as modified for use as a trainer, are all fully disclosed granted January 11,1949, to E. L. Baulch.

The antenna terminal of frequency meter 450 is connectable by a coaxial c'ablef1l'19 with the coaxlal cable junction box 419 and then through cable 442 with the coaxial junction box 441 which is located under the radiomans table or with the frequency checking terminals of the transmitter units of Figs. 6 and 8. From the junction box 416 coaxial cables 481 and 482 extend to the oscillator .unit 600 of the high reqency section and to the oscillator unit 800 of the intermediate frequency section of the long range transmitter disclosed in Figs. to 8, inclusive, where they terminate in probes enclosed within the casings of the oscillator units. The long range transmitter will be described inmore detail hereinafter. A coaxial cable 483 extends `from the coaxial 4junction box 441 where it is connected by the plug and jack connector 484, to the coaxial junction box 900 in the instructors desk to which'it makes connection by the plug and jack connector 901.

The instructors desk is provided with a control turret f1 13 mounted on the top surface thereof as schematically indicated in Fig. 1. For better in lthe Patent No, 2,458,550

illustrating the cabling from this turret to the appanatus units housed within the desk 109 the turret is shown both in front and sectional views in Fig. 9. This turret is provided with two receiver control boxes 902 and 903, a signal selector switch SS, a transmitter frequency selection switch TS, a transmitter power control switch TP and a switch TR for controlling the transfer of the desk circuits from a receiving to a transmitting condition, all mounted in the sloping portion of the front wall of the turret. A plurality of switches such as S2 and rheostats such as R2 appertaining to eight monitoring circuits, a switch IR for determining Vwhether the microphone at the desk shall be connected for operation with the interphone system or with the radio equipment, a switch yDC for connecting a 27-volt direct current :source to the `desk and a lamp DL shown immediately above it to indicate when the `direct current is connected, a switch AC for connecting a 11S-volt source of alternating current to the desk and an indicating lamp AL located immediately above it to indicate when the alternating current is thus connected, and a recall lamp RC are all mounted on the vertical portion of the front wall of the turret. These controls are best illustrated in the circuit diagram -O Fig. 10.

Four receivers are mounted in the desk. The Nos. l and 2, 904 ,and 905, are mounted on a receiver rack 906 which is in turn mounted on a frame located in the rear central portion of the desk. The Nos. 3 and 4 receivers, 901 and 908, are similarly mounted on a receiver rack 909 which is also mounted on the same frame in the desk. All of these receivers may be either locally or remotely controlled. The Vreceivers 994 yand 905 may be remotely controlled over the iiexible control cables '910 and 911 which extend from the receivers to theoontrol box 902 and the receivers :901 and 908 maybe remotely controlled over the flexible cables 912 and 913 which extend from such receivers to the control box 903.

Receivers 904 and 905 are connected by cables 914 and 915 with the control box 902, these cables making connection with the receiver rack 906 by the plug and jack connectors 916 and 911 .and with the control box by the plug and jack connectors 913 and 919. Receivers 901and 908 are similarly connected by cables 920 and 921 with the control box 903, these cables making connection with the receiver rack 909 by the plug and jack connectors 922 and 929 and with the control box 909 by the plug and jack connectors 924 and A'925. Direct current of 27 volts is supplied to these receivers from the turret over the plug and jack connector 926, cable 921 and the plug and jack connector 928 to the receiver rack 909, and over the plug and jack connector 915, cable 916, and the plug and jack connector 911 to the receiver rack 906 whereby direct current is supplied to the Nos. 3 and 4 receivers 901 and 900 from rack 909 and whereby direct current is supplied to the Nos. l and 2 receivers 904 and 905 'from rack 906. The direct current is supplied'to the turret over the plug 932 and as previously described is connectable to the circuits of the instructors desk including the cir- -cuits lextending over cables 915 and 921, under the control'ofswitch DC as best disclosed in Fig. l0. Z50-volt operating current is supplied to high voltage relay units 981, 902, 983 and 984 of the receivers from the power junction `box 933 mounted in the left `end of thedesk over the power supply cab1es'934, '935, 936 and 931 which are connected by plug and jack connectors 938, 939, 940 and 94| with the junction box 933 and by plug and jack connectors 942, 943, 944 and 945 with the receivers 904, 905, 901 and 908 respectively. These relay units are used at the desk instead of the usual dynamotor units in order that the operation of the desk may be quieter. Each unit comprises a relay operable by 27-volt direct current when the receiver to which it is allocated is turned on to connect Z50-volt direct current to the plates of the tubes of the receiver.

The inputs of the radio receivers are not connected in the usual manner with an antenna system, but instead probes are installed within the receiver casings and connected over coaxial cables 946, 941, 948 and 949 with the coaxial junction box 900 with which such cables make -connection by the plug and jack connectors 950,

95|, 952 and 953. The outputs of the receivers 904 and 905 are interconnected to A and B telephone jacks and such jacks are connected by plug-ended cords 954 and 955 with the interconnected A and B-telephone jacks of the receivers 901 and 908 and the latter jacks are further connected by plug-ended cords 956 and 951 to a terminal strip in the turret H3 from which they are connected over the cable 959 with the A and B receiver jacksv shown in Fig. 10 and mounted in the well of the desk |09.

f The receiver racks 906 and 909 are interconnected by the cable 930 and are .also connected to controls in the turret H3 over cable 960 which is plug and jack connected with the receiver rack 906 and is connected to the turret.

115-volt alternating current is supplied to the powerjunction box 933 over cable 96| which is connected to the turret H3 over the plug and jack connector 962. 115-volt alternating current is supplied to the turret under the control of switch AC over cable 963 connected to the turret over the plug and jack connector 964. From the power jun-ction box 933, 115-volt alternating current is supplied over cables 965, 966 and 961, which are connected to the junction box by plug and jack connectors 968, 969 and 910, to the Z50-volt rectier unit H00, to the regulated 220 to S50-volt rectier unit |0 and to the monitoring amplier unit H50 of Fig. 11. Also from the power junction box Z50-volt direct current is supplied over cable 91|, which is connected by the plug and jack connector 912 to the junction box, to the monitoring amplifier unit H50. 25o-volt direct currentis also. supplied to the junction box over cable 913 from the rectifier unit H0.

The coaxial junction box 900 is also connected over coaxial cable 914 with the probes of the five oscillator units ofthe radio transmitter disclosed in Fig. l2, which transmitter is located in the right end portion ofthe radio instructors desk |09.

The transmitter equipment inthe instructors desk shown in Fig. 12 consists of a shielded unit mounted on a rack in the desk with the controls mounted in the turret on the desk. The transmitteris connected to the turret by two cables of conductors such cables making connection with the transmitter over the plug and jack connectors |000 and as disclosed in Fig. 10. The trans- IriitterA consists of five oscillators, one of which is shown in full and the other four of which are similar but indicated by the boxes labeled |202 to |265, inclusive. Each of these oscillators comprises a dual oscillator tube such as OSC-l, one unit` of which may .be tuned to oscillate at one frequency and the other unit of which may be tuned to oscillate at another frequency. Thus the five oscillator units may be so tuned as to emit ten carrier frequencies covering the frequency ranges emitted by the transmitters of the airplane which the trainer is designed to simulate. The particular oscillator which is to be used for transmission is selected by the operation of the associated power supply relay of which ten I2|0 to |2|9, inclusive, are provided under the control of the ten point transmitter selector switch TS in the turret. As before stated the oscillators are connected over the coaxial cable 914 and the coaxial junction box 900 with the coaxial system.

The transmitter is also provided with a iilter section in which are mounted the filters |220 to |229, inclusive, interposed in the control conductors over which the relay l2 l0 to |2|9 are operated, the filters |230 to |234, inclusive, in the filament current supply leads to the oscillators, the filter |235 in the lainent current supply lead to the tubes ofthe modulator, the filter |236 in the supply lead over which plate potential is supplied to the tubes of the oscillators and modulator, the iilter |291 in the lead which supplies potential to the grid of the oscillator tube OSC of the modulator and the filters |238 and |239 in the operating circuit of relay |206. These lters are provided for the purpose of preventing high frequency radiation from the leads in which they are interposed.

The modulator section of the transmitter consists of a modulator tube MOD which modulates the plate potential applied to the oscillator tube which is selected for transmitting, a microphone transformer MIT which matches the microphone MIC disclosed in Fig. 10 to the modulator tube, and the modulating transformer MOT used in the output circuit of tube MOD. An audio frequency oscillator tube OSC is also provided to supply approximately 800 cycle tone for tone modulated transmission. The transmitter may be operated on CW (continuous wave) or tone or voice amplitude modulation under the control of the selector switch SS in theturret.

The conductors of cable 3|2 are extended from the junction .box |01 at the flight instructors desk over terminals of the plug and jack connector 958 to the turret H3 of the 'radio instructors desk and certain of these conductors are connected through the contacts of switches SI to S8, inclusive, and through rheostats RI and R8, inclusive, in the turret and over conductors of cable |002 to the monitoring amplier unit H50 of Fig. 11. This amplifier unit comprises a first stage having four dual amplifier tubes AMP-'4 to AMP-'1,

inclusive, and a second stage having one dual amplifier tube AMP-8. The outputs of tubes AMP-4 and AMP-5 are applied to the left unit of tube AMP-8 and the output of this unit is applied over conductor 'H5| to the A 'receiver jack |042 of the desk and the outputs of tubes AMP- 6 and AMP- 1 are applied to the right unit of tube AMP-8 and the output of this unit is applied over conductor H52 to the B receiver jack |044 of the desk. Thus when the instructors headset |003 is plugged into the jacks A and B and the proper monitoring switches of the groups SI to S9 are operated, the radio instructor is able to monitor on certain of the monitoring circuits over his left headset receiver and to monitor on others of the monitoring circuits over his right headset receiver. Plate potential of 250 volts is 7s supplied to the ampliiier tubes over cable 91| and l15volt alternating current supplied over cable 961 is applied to the step-down transformer H53 to provide 6.3-volt heating current for the filaments of the tubes.

The Z50-volt rectifier unit H00 of Fig. ll is of the well-known full wave type, 11S-volt alternating current being applied thereto over cable 005 through the switch I |04 to the primary windm ings of transformers H02 and H03. Transformer |02 is a step-up transformer and applies potential to the rectifier tube I |04 which recties the alternating current to produce direct current of 250 volts which is applied between the ground conductor I |05 and the 250-volt supply conductor I |06. The transformer i |03 is a step-down transformer for producing filament heating current of 7.5 volts in the circuit including the ground conductor H05 and heater conductor H01 for heating the filaments of the tubes of the oscillators and the oscillator and modulator tubes of the modulator shown in Fig. l2.

The 220 to 350-volt regulated rectifier unit IHO of Fig. l1 is of a well-known type having two rectifier tubes IIII and Il|2 arranged for push-pull operation, ve parallelly connected amplifier tubes IHS to III1, inclusive, connected in series with the direct current load circuit, two gas-filled tubes II I8 and IHS bridged across the load circuit and a dual tube H20, one unit of which is in bridge of the gas-filled tube HI8 and the other unit of which is in bridge of the gas-filled tube III 9. Alternating current from the 11S-volt supply source is applied over cable 956 and through switch II2I to the primary windings of transformers H22 and H23. Transformer H22 is a step-up transformer and applies its output voltage to the diode rectier tubes I I I I and III2 whereby a direct current of 350 volts is produced which is amplified by the tubes III3 to l I I1, inclusive, which are in turn regulated by the tubes HI8, III9 and H20, and applied between conductors H24 and H25 of cable 913. This potential, as previously stated is applied to the plates of the oscillatortubes of Fig. 12 and to the plates of the tubes of the radio receivers 90A, 905, 901 and 908 of Fig. 9. Transformer H23 is a step-down transformer and over its secondary windings supplies filament heating current to the filaments of tubes IHS to IIIlI, inclusive, and to the filament of tube I |20.

The apparatus disclosed within the rectangle in Fig. l0 is located at the interphone station l 01 of the flight instructors desk. It comprises ve keys I 00E. to |008, inclusive, two dual amplifier tubes |000 and IOI0 and jacks IOII, IOI2 and |0I3 into which the flight instructor may plug his vheadset IOI4 and microphone I0|5. The tubes |009 and I0|0 are supplied with filament heating current and with plate potential from suitable sources. The instructor by operating keys |004 and |005 may cause the amplification by tube |008 of signals incoming over conductors |02I and |022 of cable |020 extending from the junc- -tion box |01 of the flight instructor-s desk and the application thereof through the windings of output transformer IIJIG and over jack IOII to the left receiver of the headset IOI4 and, by operating keys |006 and |001 may cause the amplification by tube IOIc of signals incoming over 12 over the contacts of such key to conductor |025 of cable |020.

The transmitter of the trainer disclosed in Figs. 5 to 8, inclusive, is used for CW or continuous wave transmission to distant points. As previously stated this transmitter is installed in three adjoining units and is located on a pedes tal just abaft of the radiomans station. The middle unit, which provides the power supply and controls which are common to both the intermediate and high frequency units of the transmitter, comprises two removable chassis and 'H0 indicated by the two rectangles in the lower portion of Fig. 7 and non-removable panel mounted equipment disclosed in the upper portion of the figure. All conductors between the chassis |00 and the chassis 1|0 or the panel mounted equipment extend over the terminals of the plug and jack connector 10I and all conductors between the chassis 1|0 and the chassis F00 or the panel mounted equipment extend over the plug and jack connectors 1I I and 'l I2 so that the chassis may be readily removed from the frame of the unit. 27-volt direct current, 115- volt alternating current, ground connection and a side-tone conductor '|50 are connected to the middle unit of the transmitter over the plug and jack connector 15|. The middle unit is connected to the intermediate frequency unit shown in Fig. 8 by the plug and jack connectors v152 and '|53 and to the high frequency unit shown in Figs. 5 and 6 by the plug and jack connectors 154 and so that the units may be easily taken apart.

The chassis 100 comprises the high voltage power supply. Using a full Wave rectier tube 102, ll5-volt alternating current applied from power conductor 156 to the primary winding of transformer 103 is rectified and applied through the filter circuit 104 to the Z50-volt direct current supply conductor 151. The filament of tube 102 is heated by current applied thereto from the middle secondary winding of transformer '|03 and filament heating current is also applied from the upper secondary winding of transformer 103 to the filament supply conductor 1I3 of the other chassis 1|0. Chassis 100 is also provided with a transformer 105, the primary winding of which is energized from the 11S-volt power supply conductor '|56 and from the mid-point grounded secondary winding of which 671/2-volt phase ci and @a potentials are applied to the phase p1 and p2 conductors 158 and 159 for supplying the bridge circuits of the two transmitter units.

The control chassis 1|!! has mounted thereon the filament current supply transformers I I 4 and '|I5, the primary windings of which are energized from the 1l5volt alternating current supply conductor 15E. 'li-volt filament current is supplied from the secondary winding of transformer 'H5 to conductor 160 extending to the oscillator of the intermediate frequency unit of the transmitter and 15-volt filament current is supplied from the secondary windings of both transformers H4 and 1|5, connected in series, to conductor 16| extending to the oscillator of the high frequency unit of the transmitter.

Also mounted on the horizontal portion of the chassis 1I0 is a 1BGD-cycle oscillator tube OSC1, the modulator tube MOD1 for modulating the Z50-volt direct current supply of the radio-frequency oscillators of the two transmitter units, the tuning indicator tube TI, transformer TIB, output transformer 'H1 and four control relays H8, 1I8, 120 and 12|, Mounted on a vertical front portion of the chassis, and operable through an opening in the front panel of the control unit is a group of fifteen variable resistors 122 to 136 which may be adjusted to control the meter operating currents for the several tuning conditions. Relays 118, 1I9 and 120 are operable over terminals of the power control switch PCS mounted on the front panel of the unit and relay 12| is operable under the control of the tuning indicator tube TI.

Mounted on the front panel of the control unit are a meter 102 for indicating the simulated filament voltage used by either transmitter unit and a meter 153 for indicating the simulated plate current used by the transmitter unit selected for use. The filament current may be adjusted by the filament rheostat FR also mounted on the front panel. Two selector switches are also mounted on the front panel, the power control switch PCS having a first or tuning position and 1A, 1/2 and full power positions and the emission selection switch ESS. Two transmitter selection switches, having their switch arms interconnected for operation by a single switch lever, are mounted on the panel and indicated by the designation TS. A power-on switch PS is also mounted on the panel which controls the connection of :B7-volt direct current from the battery source of the trainer to conductor 164 and the connection of 115-volt alternating current from a commercial supply source to conductor 105. Four switches 166 to 109 are mounted in the lower portion of the panel which may be operated from their lower or off positions to their upper or on positions to simulate the introduction of 1, 2, 4, or microfarads alternating current voltage regulation. Immediately below these switches are four jacks 110 to 113, inclusive. The jacks 110 and 11| are connected to the winding of the keying relay 110, mounted under the top wall of the unit, which is operable in response to the closure of a telegraph key on the radiomans table plugged into jack 110. Control of a receiver relay is provided over a cord connected betwen the receiver and the receiver relay jack 11i. Jacks 112 and 113 are side-tone jacks and are connected through a fixed resistance 115 and the side-tone rheostat 116 from the left or side-tone coil of the transformer 'H8 of the circuit of oscillator tube OSC1. The high frequency side-tone jack 113 or the intermediate frequency side-tone jack 'i12 may be connected by plug ended cords to the jacl; 30 or 489 of` junction box 408 cross connected to jack M3 and jack 4l1, respectively located above the radiomans table. The volume of the tone to be heard in the radiomans headset receiver may be regulated by the rheostat 116.

Mounted in an insulating bushing on the top wall of the unit is an output terminal k18| `for the high frequency unit of the transmitter. This output terminal would ordinarily be connected to either a fixed or a trailing antenna.

The intermediate frequency-transmitter unity power supply to the apparatus on the chassis 800 interfere with nearby communication isvconnected from the terminals of the plug andl jack connectors 152 and 153 of Fig. 7 over the plug and jack connector and through filter circuits 802, 803 and 804 to the oscillator tube OSC. The filter circuits have been added for the purpose of preventing radiation from the power supply leads incoming to the oscillator over which filament current, plate potential and control grid potential are supplied to the oscillator tube. The oscillator may be tuned in the usual manner by they MQ O. vrange selector 805 under the control of an M. O. range control on the front panel of the unit and may be tuned by the M. O. tuner 806vunder the control of a tuner control on the front panel.

The shaft of the M. O. range selector 805 is connected in any suitable manner, as by a cable belt, with the shaft of an M. O'. range selector y801 mounted outside of the shield which surrounds the oscillator and the shaft of the M. O. tuner 806 is connected, as by a cable belt, with the shaft of the potentiometer 808 also mounted outside of the oscillator shield. The potentiometer shaft carries a cam 809 which is instrumental in operating the microswitch 8I0. As previously stated, a probe 8H is mounted Within the oscillator shield to pick up the output carrier frequency of the oscillator this probe being connected with the coaxial system over the coaxial cable 082. An additional probe 812 is also provided which may be connected by a temporary conductor with the frequency meter 45!)r when it is desired to check the frequency of the output of the oscillator. Conductors from the terminals of the range selector switch 801, from the winding and slider of the potentiometer 808 and from the microswitch SID are extended over terminals of the plug and jack connector BIS` to apparatus mounted on the panel of the unit.

Mounted on the panel of the intermediate frequency unit is a PA range selector switch having two sections 8M and 8|5 operable by a single panel control lever, an antenna load selector switch SIG operable by a panel control, and an antenna tuning step selector switch 8I1 operable by a panel control. Also mounted on the panel are two meters one, SIB, for indicating in amperes the simulated antenna current or radio frequency output and the other, M9, for indicating in milliamperes the grid current of the simulated power amplifier stage of the transmitter.

Mounted on a second chassis and removable from the frame of the intermediate frequency transmitter unit is the apparatus disclosed in the right portion of Fig. 8 which is provided to :enable the operation of the meters BIS and BIS in simulation of their usual response to the tuning controls of the transmitter unit. The apparatus on this chassis is connectable to the apparatus on the panel, to the apparatus on the oscillator chassis 800 and to the apparatus on the power and'control unit over the plug and jack connectory820. I Mounted on the horizontal portion of this chassis are two dual amplifier tubes 82| and822, two dual shunt diode rectifier tubes 823 and 824 anda dual `cathode follower tube 825, together withthe resistances associated therewith and the transformer 826. rIfhe transformer 826 supplies filament heating current to the tubes in a manner to be described hereinafter. Plate potential is applied to the tubes 822i, 822 and 825 from the plate voltagev supply conductor 151.

Mounted on the vertical portion of the chassis are the control relays 821 and 828 operable by the microswitch 8H) to provide antenna loading and antenna tuning discrimination, control relays 329 to 832, inclusive to provide antenna selection discrimination and control relay 833 op erable when an antenna has been selected for use. Also mounted on the vertical portion of the chassis are potentiometers 834, 835 and 33o, the slider shafts of which are aligned with and operable respectively by the regular power amu plifler tuning, antenna tuning and antenna coupling controls, which controls are mounted on the front panel of the unit. The windings of potentiometers 835, 835 and 836 are energized by potential of phase qu applied thereto from conductor 158 and the winding of potentiometer Stil is energized by potential of phase ez applied thereto from conductor 159.

. Mounted in insulators on the top wall of the cabinet of the unit are three terminals 38, 635 and 84B. Terminal 838 is normally used as the output of the power amplifier stage of the intermediate frequency transmitter unit, S39 is the fixed antenna loading input terminal and ts is the fixed antenna loading output terminal. The jumper 843 is provided for connecting the output terminal 838 of the intermediate frequency transmitter unit with the antenna loading input terminal 839. The output terminal 1st of the high frequency transmitter unit or the antenna loading output terminal 84K! of the intermediate frequency unit may be connected by a clip connector to a fixed antenna system, schematically indicated at 842, and the output terminal 181 of the high frequency transmitter unit or the out* put terminal 838 of the intermediate frequency unit may be connected to a trailing antenna system, schematically indicated at 84|.

The high frequency transmitter unit is disclosed dagrammatically in Figs. 5 and 6. The only standard equipment of this unit which has been retained is the oscillator chassis Stil, which has been carefully shielded to prevent radiation which might interfere with nearby communication work and provided with filters, and the various panel controls all of which have a distinct feel and make considerable noise when operated. The power supplied to the apparatus on the chassis Stil is connected from the terminals of the plug and jack connectors d and 155 of Fig. 7, over the plug and jack connector Sill and through the lter circuits S132, 663 and 66d to the oscillator tube OSCES. The filter circuits have been added for the purpose of preventing radiation from the power supply leads incoming to the oscillator over which filament current, plate potential and control grid potential are applied to the oscillator tube. The oscillator may be tuned in the usual manner by the M. O. range selector 605 having two range selection arcs and operable under the control of a M. O. range control on the front panel of the unit and may be tuned by the M. Ol tuner S under the control of a M. O. tuner control of the front panel.

The shaft of the M. O. range selector @t5 is connected in any suitable manner, as by a cable belt, with the shaft of a M. O. range selector 5B1 mounted outside of the shield which surrounds the oscillator and the shaft of the M. O. tuner 606 is connected, as by a cable belt, with the shaft of the potentiometer 6GB also mounted outside of the oscillator shield. As previously stated a probe 5H is mounted within the oscillator shield to pick up the output carrier frequency of the oscillator, this probe being connected with the coaxial system over the coaxial cable 81. An additional probe SI2 is also provided which may be connected by a temporary conductor with the frequency meter dit when it is desired to check the frequency of the output of the oscillator. Conductors from the terminals of the range selector switch S01 and from the winding and slider of the potentiometer Sofi are extended over terminals of the plug and jack. connector @i3 with apparatus mounted on the panel of this unit.

Mounted on the panel of the high frequency unit are three meters one, 614, for indicating in amperes the simulated antenna current or radio frequency output, the second, SI5, for indicating in milliamperes the grid current of the simun lated intermediate power amplifier stage of the transmitter and the third, SIS, for indicating in milliamperes the grid current of the simulated power amplifier stage of the transmitter. Mounted on a second chassis and removable from the frame of the high frequency transmitter unit is the apparatus disclosed in the left portion of Fig. 6 and in Fig. 5, which apparatus is provided to enable the operation of the meters 6M, Git and tit in simulation of their usual response to the tuning controls 0f the transmitter unit. The apparatus on this chassis is connectable to the apparatus on the panel, to the apparatus on the oscillator chassis ll, and to the apparatus on the power and control unit over the plug and jack connector SI1.

Mounted on a horizontal shelf portion of this chassis are three dual amplifier tubes 56B, 5cl, 592, sli-own in Fig. 5, three dual shunt diode rec-- tifier tubes 503, 5M and 535 and two dual cath-- ode follower tubes 50E and 501, together with resistances associated therewith and the transformer 508. Filament heating current for the tubes is supplied from the secondary winding of transformer 5&8 in a manner to be later de scribed. Plate potential is supplied to tubes 58E, 50i, 502, 595 and 591 from the plate voltage supply conductor 151.

Mounted on the lower end of the vertical portion of the chassis is a doubler range selector switch 518 and two doubler tuning potentiometers 5559 and 510. The shaft of the switch Sl is aligned with and connected to the doubler range tuning control mounted on the front panel of the unit. The shafts on which the sliders of the potentiometers 5&9 and 5l0 are mounted are con nected together and to the shaft of the doubler tuning control mounted on the front panel of the unit. The winding of potentiometer 505 is energized by potential of phase :p1 applied thereto from conductor 158 and the winding of potentiometer 510 is energized by potential of phase pz applied thereto from conductor 159.

Mounted on the vertical portion of the chassis jus-t below the horizontal shelf portion are two potentiometers 5H and 512 with their slider shafts interconnected and aligned with and connected to the intermediate amplifier tuning control on the front panel of the unit. The winding of potentiometer 5H is energized by potential of phase p1 applied thereto from conductor 158 and the winding of potentiometer 512 is energized by potential of phase p2 applied thereto from conductor 159. Mounted on the vertical portion of the chassis just above the potentiometers 5H and 512 is an intermediate amplifier range selector switch 619, the operating shaft of which is aligned with and connected to the in- 

